Solid-state imaging device and method for producing the same

ABSTRACT

A solid-state imaging device includes a semiconductor substrate, a light shielding section having an aperture for partially shielding light incident on a surface of the semiconductor substrate, a light reception section for converting the light which is incident on the surface of the semiconductor substrate through the aperture to an electric charge, and a passivation section having a substantially flat top surface and overlying the light shielding section, the light reception section and the aperture.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid-state imaging device, and inparticular to a solid-state imaging device structured so as to enhancethe sensitivity of a light reception section thereof and a method forproducing such a device.

2. Description of the Related Art

In recent years, the transmission and reception of images is becomingindispensable to portable information devices and the like includingcellular phones. So-called solid-state imaging devices such as CCDs areused for imaging purposes while liquid crystal panels are used fordisplaying images. In the field of solid-state imaging devices, CMOSimage sensors based on a so-called CMOS logic process, which istypically used for producing a normal integrated circuit, are widelydeveloped with a view to achieving low power consumption and a low cost.As in the case of CCDs, the demand for higher resolution andminiaturization has necessitated CMOS image sensors having reduced pixelsize, as well as having a reduced area of the light reception section,and a reduced aperture size in a light shielding film. However, sinceCMOS image sensors have so far been developed based on the so-calledlogic process, very little attention has been paid to the opticalcharacteristics of CMOS image sensors, such as reflection or refractionat interfaces between the layers of multi-layered films incorporatedtherein. Therefore, it is difficult with CMOS image sensors toefficiently converge incident light and obtain sufficient sensitivity.

A conventional solid-state imaging device, in particular a CMOS imagesensor, will be described with reference to FIG. 5. A light receptionsection 12 is formed on a top surface of a silicon substrate 11 forconverting incident light (hν) to an electric charge. An interlaminarinsulation film 13 is formed on the silicon substrate 11 forelectrically isolating a first metal layer 18, a second metal layer 19,and a light shielding film 14 from one another. The light shielding film14 is formed so as not to overlie a light reception face of the lightreception section 12, so that light incident on the interlaminarinsulation film 13 does not fall anywhere except the light receptionsection 12. A passivation film 15 is formed on the light shielding film14 and on the interlaminar insulation film 13 which is present within anaperture of the light shielding film 14. The passivation film 15provides moisture-resistance, chemical resistance, and improved barrierproperties against impurities such as Na ions, oxygen, etc., and metals.A planarization film 16 is formed on the passivation film 15. Amicrolens 17 is formed for converging light which is incident on theplanarization film 16. As the interlaminar insulation film 13, adeposited film such as a P (plasma CVD)-SiO₂ film, an NSG film (asilicon oxide film containing no impurities), a BPSG film (a siliconoxide film containing phosphorus and boron) or the like is used. As thepassivation film 15, a monolayer film, such as a P (plasma CVD)-SiNfilm, or a deposited film composed of a P-SiN film and a PSG film (asilicon oxide film containing phosphorus), is generally used. Theplanarization film 16 is generally composed of an acrylic material. Inthe case of a color solid-state imaging device, an acrylic material anda color filter are utilized as the planarization film 16. Inconventional CMOS image sensor structures, the passivation film 15 has astepped portion as described above, which prevents the convergence oflight. When such a structure is adapted for higher resolution andminiaturization, the stepped portion of the passivation film 15 causes adecrease in the amount of light converged on the light reception section12, thereby making it difficult to obtain sufficient sensitivity.

A method for producing the above-described device will now be describedwith reference to FIG. 6. The light reception section 12 is formed inthe silicon substrate 11 through ion implantation, heat treatment, etc.After forming a polycrystalline silicon film and a silicide film on thesilicon substrate 11 by using a CVD technique, a gate electrode (notshown) is formed by patterning, etching, or the like. Thereafter, a BPSGfilm is deposited as the interlaminar insulation film 13 by a CVDtechnique. When the BPSG film receives heat treatment at a hightemperature, the film becomes fluid so that its surface can beflattened. By taking advantage of such characteristics of the BPSG film,the surface of the BPSG film is flattened so as to facilitate theformation of the first metal layer 18. The first metal layer 18 isformed by depositing TiN, Al or the like on the BPSG film by using asputtering or CVD technique. Upon the first metal layer 18, the P-SiO₂film is deposited as the interlaminar insulation film 13 by using a CVDtechnique and the surface thereof is flattened by chemical machinepolishing. Thereafter, as in the case of the first metal layer 18, athin film of TiN, Al, or the like is formed as the second metal layer 19by using a sputtering or CVD technique. Similarly, upon the second metallayer 19, a P-SiO₂ film is deposited as the interlaminar insulation film13 by using a CVD technique and the surface thereof is flattened by thechemical machine polishing. Thereafter, TiN, Al, or the like isdeposited as the light shielding film 14 by using a sputtering or CVDtechnique, and the resultant film is patterned and etched so as not tooverlie the light reception section 12. Upon the light shielding film14, a P-SiN film is deposited as the passivation film 15 by using a CVDtechnique or the like. The planarization film 16 is formed by applyingan acrylic material to the passivation film 15. In the case of a colorsolid-state imaging device, an acrylic material is applied; a colorfilter is formed; and then the acrylic material is further appliedthereto as a protection coating, thereby completing the planarizationfilm 16. Thereafter, a lens material is applied and the microlens 17 isformed by patterning and heat treatment.

In a conventional solid-state imaging device shown as FIG. 5A, therefractive index of the P-SiN film used for the passivation film 15 isabout 2.0 while the refractive index of the acrylic material used forthe planarization film 16 is about 1.5 to 1.6. In the case where therefractive index of the passivation film 15 is higher than that of theplanarization film 16, when light falls onto an edge of the passivationfilm 15, the incident light is not converged on the light receptionsection 12 but rather refracted so as to travel outside the lightreception section 12 toward the first metal layer 18 or the second metallayer 19 since the edge of the passivation film 15 has a rounded shape.As shown in an enlarged view of FIG. 5B, when light falls onto the flattop surface of the stepped portion, total internal reflection can occurat an interface between the planarization film 16 and a face of thepassivation film 15 parallel to a side face of the light shielding film14, depending on the incident angle of the light, since the refractiveindex of the passivation film 15 is higher than that of theplanarization film 16. The incident light passes along the face of thepassivation film 15 parallel to the side face of the light shieldingfilm 14 so that the light is not converged on the light receptionsection 12. As described above, in the conventional structure shown asFIG. 5A, any light incident on a portion of the passivation film 15neighboring the side face of the light shielding film 14 is notconverged on the light reception section 12. Therefore, the effectiveaperture size of the light shielding film 14 is smaller than the actualaperture size by an amount corresponding to the thickness of thepassivation film 15.

The light reception face of the light reception section 12 used to besufficiently large relative to the stepped portion of the passivationfilm 15. However, due to the reduced pixel size which is necessitatedfor improved resolution and miniaturization, the light reception face ofthe light reception section 12 is becoming smaller and the aperture ofthe light shielding film 14 is also becoming narrower. Therefore, theratio of the amount of light incident on the stepped portion of thepassivation film 15 to the amount of light incident on the aperture ofthe light shielding film 14 increases, thereby making it difficult toobtain sufficient sensitivity. However, the passivation film 15 can notbe omitted because the passivation film 15 plays an important role inproviding moisture-resistance, chemical resistance and/or improvedbarrier properties against impurities such as Na ions, oxygen, etc., andmetals.

The effect of the stepped portion of the passivation film 15 on thenumerical aperture of the light shielding film 14 will now be describedin detail. Provided that the sensitivity deteriorates by an amountcorresponding to the thickness of the passivation film 15, the aperturesize can be represented as (pixel size)−(width of the light shieldingfilm)−(2×thickness of the passivation film 15). For example, in the casewhere the width of the light shielding film 14 is 1.5 μm, and thethickness of the passivation film 15 is 0.5 μm, given a pixel size of 10μm×10 μm, the aperture of the light shielding film 14 is calculated tobe 10−1.5−(0.5×2)=7.5 μm, and therefore, the numerical aperture is 75%.Similarly, given a pixel size of 5 μm×5 μm, the aperture of the lightshielding film 14 is calculated to be 5−1.5−(0.5×2)=2.5 μm, andtherefore, the numerical aperture is 50%. Starting from the aboveone-dimensional calculation, it will be seen that the numerical aperturearea as calculated in a two-dimensional manner gives rise to an evengreater difference in the size (area) between the aperture and eachpixel. The reduction in the numerical aperture of the light shieldingfilm 14 is highly detrimental to the ratio of light incident on thelight reception face of the light reception section 12; this effect ismore detrimental than any reduction in the numerical aperture of layersbelow the light shielding film 14.

SUMMARY OF THE INVENTION

According to one aspect of this invention, there is provided asolid-state imaging device, including a semiconductor substrate, a lightshielding section having an aperture for partially shielding lightincident on a surface of the semiconductor substrate, a light receptionsection for converting the light which is incident on the surface of thesemiconductor substrate through the aperture to an electric charge, anda passivation section having a substantially flat top surface andoverlying the light shielding section, the light reception section andthe aperture.

According to one embodiment of the invention, the passivation sectionincludes at least a silicon nitride-based monolayer film.

According to another embodiment of the invention, a solid-state imagingdevice further includes an insulation section having a substantiallyflat top surface which is interposed between the passivation section andthe light shielding section.

According to still another embodiment of the invention, the insulationsection includes at least a silicon oxide-based monolayer film.

According to another aspect of the invention, there is provided a methodfor producing a solid-state imaging device which includes asemiconductor substrate, a light shielding section having an aperturefor partially shielding light incident on a surface of the semiconductorsubstrate, a light reception section for converting the light which isincident on the surface of the semiconductor substrate through theaperture to an electric charge, and a passivation section having asubstantially flat top surface and overlying the light shieldingsection, the light reception section and the aperture, and the methodincludes the steps of forming a thin film used for forming thepassivation section on the light shielding section and the aperture, andflattening a surface of the thin film to form the passivation section bychemical machine polishing.

According to still another aspect of the invention, there is provided amethod for producing a solid-state imaging device which includes asemiconductor substrate, a light shielding section having an aperturefor partially shielding light incident on a surface of the semiconductorsubstrate, a light reception section for converting the light which isincident on the surface of the semiconductor substrate through theaperture to an electric charge, and a passivation section having asubstantially flat top surface and overlying the light shieldingsection, the light reception section and the aperture, and the methodincludes the steps of forming a thin film used for forming thepassivation section on the light shielding section, applying an SOG filmto the thin film used for forming the passivation section, andperforming an etchback technique under a condition that a selectiveratio of the SOG film to the thin film used for forming the passivationsection is about 1 to 1.

According to still another aspect of the invention, there is provided amethod for producing a solid-state imaging device which includes asemiconductor substrate, a light shielding section having an aperturefor shielding light incident on a surface of the semiconductorsubstrate, a light reception section for converting the light which isincident on the surface of the semiconductor substrate through theaperture to an electric charge, a passivation section having asubstantially flat top surface and overlying the light shieldingsection, the light reception section and the aperture, and an insulationsection having a substantially flat top surface which is interposedbetween the passivation section and the light shielding section, and themethod includes the steps of forming the insulation section on the lightshielding section, flattening a surface of the insulation section bychemical machine polishing, and forming the passivation section so as tohave the substantially flat top surface by depositing a material usedfor forming the passivation section on the insulation section.

According to still another aspect of the invention, there is provided amethod for producing a solid-state imaging device which includes asemiconductor substrate, a light shielding section having an aperturefor partially shielding light incident on an surface of thesemiconductor substrate, a light reception section for converting thelight which is incident on the surface of the semiconductor substratethrough the aperture to an electric charge, a passivation section havinga substantially flat top surface and overlying the light shieldingsection, a light reception section and the aperture, and an insulationsection having a substantially flat top surface which is interposedbetween the passivation section and the light shielding section, and themethod includes the steps of forming the insulation section so as tohave the substantially flat top surface by applying an SOG film to thelight shielding section and the aperture, and forming the passivationsection so as to have the substantially flat top surface by depositing amaterial used for forming the passivation section on the insulationsection.

In order to achieve the above-described objectives, according to thepresent invention, a passivation film is deposited on an interlaminarinsulation film so as to have a thickness which is greater than that ofa light shielding film. Thereafter, a portion of the thickly depositedpassivation film is removed, to such an extent that the light shieldingfilm is not exposed, by chemical machine polishing or by using anetchback technique after applying an SOG to the passivation film. Thus,a surface of the passivation film is flattened.

Alternatively, a silicon oxide-based insulation film is thicklydeposited on the light shielding film and the interlaminar insulationfilm in the manner described above. Thereafter, a portion of theresultant film is removed, to such an extent that the light shieldingfilm is not exposed, by using chemical machine polishing. Thus, asurface of the film is flattened. A passivation film is then depositedon a top surface of the silicon oxide-based insulation film. Since thetop surface of the silicon oxide-based insulation film is flat, the topsurface of the passivation film, which is deposited on the insulationfilm, also becomes flat. Therefore, the passivation film is preventedfrom having any stepped portion, which is one problem associated with aconventional passivation film.

Alternatively, an SOG film is applied on the light shielding film andthe interlaminar insulation film. The passivation film is then depositedon a top surface of the SOG film. Since the top surface of the SOG filmis flat, the top surface of the passivation film, which is deposited onthe SOG film, also becomes flat. Therefore, the passivation film isprevented from having any stepped portion, which is one problemassociated with a conventional passivation film.

As described above, through the use of the aforementioned techniques,according to the present invention, the passivation film is preventedfrom having any stepped portion, which is one problem associated with aconventional passivation film. Therefore, a component of light whichwould otherwise fall onto stepped areas to be refracted in directionsaway from the light reception section can be converged on the lightreception section. Thus, the imaging device according to the presentinvention can be adapted for higher resolution and miniaturization.

Thus, the invention described herein makes possible the advantages of:(1) providing a solid-state imaging device which can converge incidentlight on a light reception section thereof due to the absence of steppedportions on a passivation film; and (2) providing a method for producingsuch a solid-state imaging device.

These and other advantages of the present invention will become apparentto those skilled in the art upon reading and understanding the followingdetailed description with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a solid-state imaging deviceaccording to Example 1 of the present invention.

FIG. 2 is a cross-sectional view of a solid-state imaging deviceaccording to Example 2 of the present invention.

FIGS. 3A, 3B, 3C, 3D, 3E, and 3F are cross-sectional views illustratingproduction steps of a solid-state imaging device according to Example 1of the present invention.

FIGS. 4A, 4B, 4C, 4D, 4E, 4F and 4G are cross-sectional viewsillustrating production steps of a solid-state imaging device accordingto Example 2 of the present invention.

FIG. 5A is a cross-sectional view illustrating a structure of aconventional solid-state imaging device.

FIG. 5B is a partial enlarged view of FIG. 5A.

FIGS. 6A, 6B, 6C, 6D, 6E, and 6F are cross-sectional views illustratingproduction steps of a conventional solid-state imaging device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Examples of the present invention will be described below in detail withreference to drawings.

EXAMPLE 1

A basic structure of Example 1 of the present invention is shown in FIG.1. As shown in FIG. 1, a light reception section 2 for convertingincident light to an electric charge is formed on a top surface of asilicon substrate 1. An interlaminar insulation film 3 for electricallyisolating a first metal layer 8, a second metal layer 9, and a lightshielding film 4 from one another is formed on the silicon substrate 1.The light shielding film 4 is formed on the interlaminar insulation film3 without overlying, a light reception face of the light receptionsection 2, so that incident light does not fall anywhere except thelight reception section 2. A passivation film 5 is formed on the lightshielding film 4 and on the interlaminar insulation film 3 which ispresent within an aperture of the light shielding film 4 in order toprovide moisture-resistance, chemical resistance, and improved barrierproperties against impurities such as Na ions, oxygen, etc., and metals.A portion of the passivation film 5 is removed, to such an extent thatthe light shielding film 4 is not exposed, by using chemical machinepolishing or an etchback technique. Thus a surface of the passivationfilm is flattened. A planarization film 6 is formed on the passivationfilm 5. A microlens 7 is formed for converging light which is incidenton the planarization film 6. In Example 1, the passivation film 5 may bein the form of a SiN-based monolayer film, or a deposited film composedof a SiN-based film, having a refractive index of about 2.0. An acrylicmaterial is used for the planarization film 6, having a refractive indexof about 1.5 to 1.6.

In conventional structures, the passivation film 15 would have a steppedportion as shown in FIGS. 5A and 5B. Light incident on the steppedportion is refracted in directions away from the light receptionsection, due to the different refractive index of an edge of the steppedportion. Since the refractive index of the passivation film 15 is higherthan that of the planarization film 16, total internal reflection occursat an interface between the planarization film 16 and a face of thepassivation film 15 parallel to a side face of the light shielding film14, so that incident light is not converged on the light receptionsection 12. However, in the structure according to Example 1 of thepresent invention, the passivation film 5 is thickly deposited and a topsurface thereof is flattened by chemical machine polishing or anetchback technique, so that any refraction of incident light associatedwith a stepped portion, as in the case of the passivation film 15 ofconventional structures, does not occur. As a result, most of lightconverged by the microlens 7 is converged on the light reception section2.

A method for producing a solid-state imaging device according to Example1 of the present invention will now be described with reference to FIGS.3A, 3B, 3C, 3D, 3E, and 3F. The light reception section 2 is formed inthe silicon substrate 1 through ion implantation, heat treatment, etc.(FIG. 3A). After forming a polycrystalline silicon film and a silicidefilm on the silicon substrate 1 by using a CVD technique, a gateelectrode (not shown) is formed by patterning, etching, or the like.Thereafter, a BPSG film is deposited so as to have a thickness of about5000 Å to 15000 Å as the interlaminar insulation film 3 by a CVDtechnique. By subjecting the BPSG film to heat treatment at about 850 to950° C., its surface is flattened so as to facilitate the formation ofthe first metal layer 8. The first metal layer 8 is formed by depositingTiN to a thickness of about 300 Å to 1000 Å and Al to a thickness ofabout 3000 Å to 10000 Å on the BPSG film by using a sputtering or CVDtechnique (FIG. 3B). Upon the first metal layer 8, a P-SiO₂ film havinga thickness of about 20000 Å to 25000 Å is deposited as the interlaminarinsulation film 3 by using a CVD technique, and a thickness of about10000 Å is removed from the resultant film by chemical machinepolishing, thereby flattening the film surface. Thereafter, as in thecase of the first metal layer 8, TiN having a thickness of about 300 Åto 1000 Å and Al having a thickness of about 3000 Å to 10000 Å aredeposited as the second metal layer 9 by using a sputtering or CVDtechnique (FIG. 3C). Similarly, upon the second metal layer 9, a P-SiO₂film having a thickness of about 20000 Å to 25000 Å is deposited as theinterlaminar insulation film 3 by using a CVD technique and a thicknessof about 10000 Å is removed from the resultant film by chemical machinepolishing, thereby flattening the film surface. Thereafter, TiN having athickness of about 300 Å to 1000 Å and Al having a thickness of about3000 Å to 10000 Å are deposited as the light shielding film 4 by using asputtering or CVD technique, and the resultant film is patterned andetched so as not to overlie the light reception section 2 (FIG. 3D).Upon the light shielding film 4, a P-SiN film having a thickness of20000 Å is deposited as the passivation film 5. Thereafter, a thicknessof about 10000 Å is removed from the P-SiN film by chemical machinepolishing, thereby flattening the film surface (FIG. 3E). In another wayof flattening, conventional production steps are used so as to form thelight shielding film 4, and thereafter, a P-SiN layer is thicklydeposited as the passivation film 5 by using a CVD technique or thelike.

Thereafter, SOG is applied to a top surface of the passivation film 5and a top surface of the resultant film is etched by using an RIE underan etching condition such that the selectivity ratio of the P-SiN to theSOG is about 1:1, thereby flattening the top surface of the passivationfilm 5. More particulaly, the light shielding film 4 is deposited so asto have a thickness of about 3000 Å to 10000 Å, and a P-SiN film havinga thickness of about 20000 Å is deposited as the passivation film 5. SOGis applied to the P-SiN film so as to have a thickness of about 15000 Å.A 1:1 selectivity ratio of P-SiN to SOG can be obtained under thefollowing RIE etching conditions: pressure: 4 to 15 Pa; CHF₃: 20 to 50sccm; CF₄: 20 to 50 sccm; Ar: 50 to 100 sccm: O₂: 1 to 5 sccm; and RF:200 to 700 W. By performing etching under such conditions, the topsurface of the P-SiN film can be flattened (FIG. 3E). After flatteningthe top surface of the passivation film 5, a planarization film 6 isformed by applying an acrylic material to the passivation film 5. In thecase of a color solid-state imaging device, an acrylic material isapplied; a color filter is formed; and then the acrylic material isfurther applied thereto as a protection coating, thereby completing theplanarization film 6. Thereafter, a lens material is applied to theplanarization film 6, and the microlens 7 is formed by patterning andheat treatment (FIG. 3F).

Since the stepped portions of the passivation film 5 are eliminated, theaperture of the light shielding film 4 can be represented as (pixelsize)−(width of light shielding film). For example, in the case wherethe width of the light shielding film 4 is 1.5 μm, given a pixel size of5 μm×5 μm, the aperture of the light shielding film 4 is calculated tobe 5−1.5=3.5 μm, and therefore, the numerical aperture is 70%. Since theconventional numerical aperture is 50%, the numerical aperture of thepresent example is improved so as to be 1.4 times the conventionalnumerical aperture.

EXAMPLE 2

Example 2 of the present invention will now be described.

A basic structure of Example 2 of the present invention is shown in FIG.2. As shown in FIG. 2, a light reception section 2 for convertingincident light to an electric charge is formed on a top surface of asilicon substrate 1. An interlaminar insulation film 3 for electricallyisolating a first metal layer 8, a second metal layer 9, and a lightshielding film 4 from one another is formed on the silicon substrate 1.The light shielding film 4 is formed on the interlaminar insulation film3 without overlying a light reception face of the light receptionsection 2, so that incident light does not fall anywhere except thelight reception section 2. A silicon oxide film 10 is formed on thelight shielding film 4 and on the interlaminar insulation film 3 whichis present within an aperture of the light shielding film 4. A portionof the silicon oxide film 10 is removed, to such an extent that thelight shielding film 4 is not exposed, by using chemical machinepolishing. Thus a surface of the silicon oxide film 10 is flattened.When the silicon oxide film 10 is formed by application of SOG, asilicon oxide film having a flat top surface can be formed withoutperforming chemical machine polishing. A passivation film 5 is formed onthe silicon oxide film 10 in order to provide moisture-resistance,chemical resistance, and improved barrier properties against impuritiessuch as Na ions, oxygen, etc., and metals. A planarization film 6 isformed on the passivation film 5. A microlens 7 is formed for converginglight which is incident on the planarization film 6.

In Example 2, because it is more advantageous to flatten the top surfaceof the silicon oxide-based film than to flatten the top surface of theP-SiN film, it is easier to apply chemical machine polishing to thesilicon oxide film 10 than to the P-SiN passivation film 5 for thefollowing reasons. Firstly, a silicon oxide-based film can be relativelyeasily etched since its etching rate is faster than that of the P-SiNfilm. Secondly, since chemical machine polishing is performed at thetime of forming the interlaminar insulation film 3, a conventionalchemical machine polishing technique can be applied to the siliconoxide-based film. Since the passivation film 5 is deposited on thesilicon oxide film 10 after the top surface of the silicon oxide film 10is flattened, a top surface of the passivation film 5 can also beflattened. Thus, the stepped portion of the passivation film 5 shown inFIG. 5A can be eliminated, so that light which is converged by themicrolens 7 on the light reception section 2 can be converged withoutbeing obstructed.

A method for producing a solid-state imaging device according to Example2 will now be described with reference to FIG. 4. Production steps ofthe conventional method and Example 1 are used in Example 2 so as toform the light shielding film 4. The light reception section 2 is formedin the silicon substrate 1 through ion implantation, heat treatment,etc. (FIG. 4A). After forming a polycrystalline silicon film and asuicide film on the silicon substrate 1 by using a CVD technique, a gateelectrode (not shown) is formed by patterning, etching, or the like.Thereafter, a BPSG film having a thickness of about 5000 Å to 15000 Å isdeposited as the interlaminar insulation film 3 by a CVD technique. Bysubjecting the BPSG film to heat treatment at about 850 to 950° C., itssurface is flattened so as to facilitate the formation of the firstmetal layer 8. The first metal layer 8 is formed by depositing TiN to athickness of about 300 Å to 1000 Å and Al to a thickness of about 3000 Åto 10000 Å on the BPSG film by using a sputtering or CVD technique (FIG.4B). Upon the first metal layer 8, a P-SiO₂ film having a thickness ofabout 20000 Å to 25000 Å is deposited as the interlaminar insulationfilm 3 by using a CVD technique, and a thickness of about 10000 Å isremoved from the P-SiN film by chemical machine polishing, therebyflattening the film surface. Thereafter, as in the case of the firstmetal layer 8, TiN having a thickness of about 300 Å to 1000 Å and Alhaving a thickness of about 3000 Å to 10000 Å are deposited as thesecond metal layer 9 by using a sputtering or CVD technique (FIG. 4C).Similarly, upon the second metal layer 9, a P-SiO₂ film having athickness of about 20000 Å to 25000 Å is deposited as the interlaminarinsulation film 3 by using a CVD technique, and a thickness of about10000 Å is removed from the P-SiO₂ film by chemical machine polishing,thereby flattening the film surface. Thereafter, TiN having a thicknessof about 300 Å to 1000 Å and Al having a thickness of about 3000 Å to10000 Å are deposited as the light shielding film 4 by using asputtering or CVD technique, and the resultant film is patterned andetched so as not to overlie the light reception section 2 (FIG. 4D). Asdescribed above, production steps of the conventional method are used soas to form the light shielding film 4. Thereafter, the silicon oxidefilm 10 having a thickness of about 20000 Å to 25000 Å is deposited byusing a CVD technique and a thickness of about 10000 Å is removed fromthe resultant film by a chemical machine polishing (FIG. 4E).Thereafter, a P-SiN film 5 having a thickness of about 3000 Å to 10000 Åis deposited on the silicon oxide film 10, thereby flattening a topsurface of the P-SiN film 5 (FIG. 4F).

In another way of flattening, conventional production steps are used soas to form the light shielding film 4, and thereafter, SOG is applied tothe light shielding film 4 as the silicon oxide film 10 (FIG. 4E). AP-SiN film 5 is deposited on the flattened silicon oxide film 10, whichis formed of an SOG film, so as to obtain the P-SiN film 5 having a flattop surface (FIG. 4F). In this case, the applied SOG film has athickness of about 10000 Å to 15000 Å, and the P-SiN film 5 having athickness of about 3000 Å to 10000 Å is deposited by a CVD technique.Thereafter, the planarization film 6 is formed by applying an acrylicmaterial to the P-SiN film 5. In the case of a color solid-state imagingdevice, an acrylic material is applied; a color filter is formed; andthen the acrylic material is further applied thereto as a protectioncoating, thereby completing the planarization film 6. Thereafter, a lensmaterial is applied thereto and the microlens 7 is formed by patterningand heat treatment (FIG. 4G).

As described above, according to the present invention, the steppedportion can be eliminated by flattening a top surface of the passivationfilm, so that incident light can be converged on the light receptionsection. Therefore, the present invention makes it possible to provide asolid-state imaging device which is capable of efficiently convergingincident light on a light reception section thereof so as to be adaptedfor reduced pixel size.

Various other modifications will be apparent to and can be readily madeby those skilled in the art without departing from the scope and spiritof this invention. Accordingly, it is not intended that the scope of theclaims appended hereto be limited to the description as set forthherein, but rather that the claims be broadly construed.

1. A solid-state imaging device, comprising: a semiconductor substrate;a light shielding section having an aperture for partially shieldinglight incident on a surface of the semiconductor substrate; a lightreception section for converting the light which is incident on thesurface of the semiconductor substrate through the aperture to anelectric charge; a single, continuous thin film used as a passivationsection having a substantially flat top surface and a refractive indexand overlying the light shielding section, the light reception sectionand the aperture; and a planarization section overlying thesubstantially flat top surface of said thin film used as a passivationsection, wherein the planarization section has a refractive indexsmaller than the refractive index of the thin film used as a passivationsection.
 2. A solid-state imaging device according to claim 1, whereinthe thin film used as a passivation section comprises at least a siliconnitride-based monolayer film.
 3. A solid-state imaging device accordingto claim 1, further comprising an insulation section having asubstantially flat top surface which is interposed between the thin filmused as a passivation section and the light shielding section.
 4. Asolid-state imaging device according to claim 3, wherein the insulationsection comprises at least a silicon oxide-based monolayer film.
 5. Asolid-state imaging device according to claim 4, wherein the insulationsection comprises at least a SOG film.
 6. A solid-state imaging deviceaccording to claim 1, wherein the thin film used as a passivationsection comprises at least a SOG film.
 7. A method for producing asolid-state imaging device, wherein the device comprises: asemiconductor substrate; a light shielding section having an aperturefor partially shielding light incident on a surface of the semiconductorsubstrate; a light reception section for converting the light which isincident on the surface of the semiconductor substrate through theaperture to an electric charge; a single, continuous passivation sectionhaving a substantially flat top surface and overlying the lightshielding section, the light reception section and the aperture; and aplanarization section overlying the substantially flat top surface ofsaid passivation section, wherein the planarization section has arefractive index smaller than the refractive index of the passivationsection, wherein the method comprises the steps of: forming a single,continuous thin film used for forming the passivation, section on thelight shielding section and the aperture; flattening a surface of thesingle, continuous thin film to form the passivation section by chemicalmachine polishing; and forming a thin film used for forming theplanarization section atop the substantially flat top surface of thepassivation section; and flattening a surface of the thin film used forforming the passivation section by chemical machine polishing.
 8. Amethod according to claim 7, wherein the method further comprises thestep of forming a SOG film to the thin film used as a passivationsection.
 9. A method for producing a solid-state imaging device, whereinthe device comprises: a semiconductor substrate; a light shieldingsection having an aperture for partially shielding light incident on asurface of the semiconductor substrate; a light reception section forconverting the light which is incident on the surface of thesemiconductor substrate through the aperture to an electric charge; anda passivation section having a substantially flat top surface andoverlying the light shielding section, the light reception section andthe aperture so as to provide moisture and chemical resistance and toprovide barrier properties against impurities, wherein the methodcomprises the steps of: forming a thin film used for forming thepassivation section on the light shielding section; applying an SOG filmto the thin film used for forming the passivation section; andflattening a surface of the thin film to form the passivation section byperforming an etchback technique under a condition that a selectiveratio of the SOG film to the thin film used for forming the passivationsection is about 1:1.
 10. A method for producing a solid-state imagingdevice, wherein the device comprises: a semiconductor substrate; a lightshielding section having an aperture for partially shielding lightincident on a surface of the semiconductor substrate; a light receptionsection for converting the light which is incident on the surface of thesemiconductor substrate through the aperture to an electric charge; asingle, continuous thin film used as a passivation section having asubstantially flat top surface and a reflective index and overlying thelight shielding section, the light reception section and the aperture soas to provide moisture and chemical resistance and to provide barrierproperties against impurities, and an insulation section having asubstantially flat top surface which is interposed between the thin filmused as a passivation section and the light shielding section; and aplanarization section overlying the substantially flat top surface ofsaid thin film used as a passivation section, wherein the planarizationsection has a refractive index smaller than the refractive index of thethin film used as a passivation section, wherein the method comprisesthe steps of: forming the insulation section on the light shieldingsection; flattening a surface of the insulation section by chemicalmachine polishing; forming the thin film used as a passivation sectionso as to have the substantially flat top surface by depositing amaterial used for forming the passivation section on the insulationsection; and forming the planarization section by depositing a materialused for forming the planarization section on the substantially flat topsurface of the thin film used as a passivation section.
 11. A methodaccording to claim 10, wherein the method further comprises the step offorming a SOG film to the thin film used as a passivation section.
 12. Amethod for producing a solid-state imaging device, wherein the devicecomprises: a semiconductor substrate; a light shielding section havingan aperture for partially shielding light incident on a surface of thesemiconductor substrate; a light reception section for converting thelight which is incident on the surface of the semiconductor substratethrough the aperture to an electric charge; a single, continuous thinfilm used as a passivation section having a substantially flat topsurface and a reflective index and overlying the light shieldingsection, a light reception section and the aperture; a planarizationsection overlying the substantially flat top surface of said thin filmused as a passivation section, wherein the planarization section has arefractive index smaller than the refractive index of the thin film usedas a passivation section; and an insulation section having asubstantially flat top surface which is interposed between the thin filmused as a passivation section and the light shielding section so as toprovide moisture and chemical resistance and to provide barrierproperties against impurities, wherein the method comprises the stepsof: forming the insulation section so as to have the substantially flattop surface by applying an SOG film to the light shielding section andthe aperture; and forming the single, continuous thin film used as apassivation section so as to have the substantially flat top surface bydepositing a material used for forming the single, continuous thin filmused as a passivation section on the insulation section; and forming theplanarization section by depositing a material used for forming theplanarization section on the substantially flat top surface of the thinfilm used as a passivation section.
 13. A solid-state imaging device,comprising: a semiconductor substrate; a light shielding section havingan aperture for partially shielding light incident on a surface of thesemiconductor substrate; a light reception section for converting thelight which is incident on the surface of the semiconductor substratethrough the aperture to an electric charge; and a single, continuousthin film used as a passivation section having a substantially flat topsurface and overlying the light shielding section, the light receptionsection and the aperture so as to provide moisture and chemicalresistance and to provide barrier properties against impurities andothers.
 14. A method for producing a solid-state imaging device, whereinthe device comprises: a semiconductor substrate; a light shieldingsection having an aperture for partially shielding light incident on asurface of the semiconductor; a light reception section for convertingthe light which is incident on the surface of the semiconductorsubstrate through the aperture to an electric charge; and a single,continuous passivation section having a substantially flat top surfaceand overlying the light shielding section, the light reception sectionand the aperture so as to provide moisture and chemical resistance andto provide barrier properties against impurities and others, wherein themethod comprises the steps of: forming a single, continuous thin filmused for forming the passivation section on the light shielding sectionand the aperture; and flattening a surface of the single, continuousthin film to form the passivation section by chemical machine polishing.15. A solid-state imaging device, comprising: a semiconductor substrate;a light shielding section having an aperture for partially shieldinglight incident on a surface of the semiconductor substrate; a lightreception section for converting the light which is incident on thesurface of the semiconductor substrate through the aperture to anelectric charge; a passivation section having a substantially flat topsurface and a refractive index and overlying the light shieldingsection, the light reception section and the aperture; and aplanarization section overlying the substantially flat top surface ofsaid passivation section, wherein the planarization section has arefractive index smaller than the refractive index of the passivationsection, wherein a selection ratio of the planarization section to thepassivation section is about 1:1.
 16. A solid-state imaging deviceaccording to claim 15, wherein the passivation section comprises atleast a silicon nitride-based monolayer film.
 17. A solid-state imagingdevice according to claim 15, further comprising an insulation sectionhaving a substantially flat top surface which is interposed between thepassivation section and the light shielding section.
 18. A solid-stateimaging device according to claim 17, wherein the insulation sectioncomprises at least a silicon oxide-based monolayer film.
 19. Asolid-state imaging device according to claim 18, wherein the insulationsection comprises at least a SOG film.
 20. A solid-state imaging deviceaccording to claim 15, wherein the passivation section comprises atleast a SOG film.